§ 3.7 - DC-coupled 8 Channel Stereo Mixer
Back to → Main Mixer Block Page
Before you attempt this build, please:
- Read through the numbered build procedure with the idea of performing the listed steps in order
Examine the PCB layout
Examine the schematic diagram
Refer to each of the linked pages in the "See also" list
This will help ensure that you will have the best possible experience, resulting in a build that works the way you expect it to.
This Mixer Block build is a DC-coupled, unity-gain, line-level, eight-channel, stereo mixer.
To power this with the Power Block, use the +/- 12 regulated Power Block build.
Unity gain (zero gain) is important here. This is because if all eight inputs to one of the op-amp channels reach 1.23
volts, in phase, all at once, then at unity gain the mixer will produce a 9.84
volt output level. This would be highly unlikely, but it is always at least possible.
If the mixer were to be built with more gain, then the output voltage would get too close to the op-amp's power supply rails (typically +/- 12 VDC
), and distortion would result.
C1—C2: .1 uF ceramic capacitor
C3—C4 optional: ceramic capacitors, only needed for op-amps that require compensation
TLO-72 and TLO-82 op-amps do not require compensation.
C21—C22: 10 uF ceramic or other non-polarized capacitor
R1—R18: 10 k-ohms 1/8th watt resistors
Install 3-pin jumper J1 — use .100 inch (2.54 mm) header pins; do not close
Install 2-pin jumper J2 — use .100 inch (2.54 mm) header pins; do not close
Install 2-pin jumper J3 — use .100 inch (2.54 mm) header pins; close with a header jumper cap
Install 2-pin jumper J4 — use .100 inch (2.54 mm) header pins; close with a header jumper cap
U1: TLO-72 low-noise op-amp, can substitute TLO-82, or similar. Observe polarity. An IC socket is strongly recommended.
Connectors, quantity 4, optional: 5.08mm (.200 in) Spacing, 2-pin PCB Mount Screw Terminal Blocks
M3 mounting hardware, 4 mount points
If you would like to AC
-couple the outputs while retaining the DC
input coupling, remove the jumper caps from J
3 and J
DC-coupled 8-channel Stereo Mixer, Build Guide
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